Acicular alpha-iron particles - produced by reducing a mixt. of alpha-iron oxide hydrate and calcium oxide

摘要

Prodn. of acicular alpha-iron particles comprises (a) mixing acicular alpha-FeOOH particles with CaO in a CaO/alpha-FeOOH wt. ratio of 1.5-5:1 (pref. 3-4:1); (b) contacting the mixt. with H2 at 150-350 degrees C (pref. 150-250 degrees C) and 1-1000 (pref. 450-500) atmos.; and (c) sepg. the alpha-iron particle from the the reaction mixt. Also claimed are acicular alpha-iron particles with a length of 1 mu, a coercivity of >=800 Oe, an alpha-Fe content of 70 (pref. 75-95) wt.%, and contg. surface Ca2+ ions (detectable by emission spectroscopy). The products are esp. suitable for use in magnetic memory elements (esp. magnetic tapes). The Ca2+ -contg. coating on the particles inhibits loss of acicularity during the redn. step.